Firebase Cloud Functions cannot read nitro generated index.mjs file

EDIT:

I want to deploy a Nuxt3 app to Firebase Hosting. I've set the deployment preset for Nitro to "firebase" NITRO_PRESET=firebase, and the build step works fine. However, when I run firebase deploy, I get an error saying:

There was an error reading .output/server/package.json: 
.output/server/index.js does not exist, can't deploy Cloud Functions

I checked the .output/server directory, and saw that Nitro generated a file called index.mjs. I checked to see if Cloud Functions also works with .mjs files, but that doesn't seem to be the case. I looked for possible solutions but couldn't find anything; I tried reinstalling my modules, but no luck. Do I have something misconfigured or broken?

I'm following this tutorial: https://nitro.unjs.io/deploy/providers/firebase

I'm using WSL2 Ubuntu on Windows 11, and the project folder is inside the linux filesystem.

Here is my package.json:

{
  "private": true,
  "scripts": {
    "build": "nuxt build",
    "dev": "nuxt dev",
    "generate": "nuxt generate",
    "preview": "nuxt preview"

  },
  "devDependencies": {
    "@nuxtjs/google-fonts": "^3.0.0-0",
    "@types/three": "^0.143.1",
    "nuxt": "3.0.0-rc.8"
  },
  "dependencies": {
    "firebase": "^9.9.3",
    "sass": "^1.54.5",
    "three": "^0.143.0",
    "vuex": "^4.0.2",
    "sass-loader": "^13.0.2"
  }
}

My firebase.json:

{
  "functions": {
    "source": "./.output/server",
    "runtime": "nodejs16",
    "ignore": [
      "node_modules",
      ".git",
      "firebase-debug.log",
      "firebase-debug.*.log"
    ]
  },
  "hosting": {
    "site": "my-site",
    "public": ".output/public",
    "ignore": [
      "firebase.json",
      "**/.*",
      "**/node_modules/**"
    ],
    "cleanUrls": true,
    "rewrites": [
      {
        "source": "**",
        "function": "server"
      }
    ]
  }
}

After the build step:

Σ Total size: 19.6 MB (3.21 MB gzip)
✔ You can deploy this build using npx firebase deploy                 

After the deployment step:

i  deploying functions, hosting
i  functions: ensuring required API cloudfunctions.googleapis.com is enabled...
i  functions: ensuring required API cloudbuild.googleapis.com is enabled...
i  artifactregistry: ensuring required API artifactregistry.googleapis.com is enabled...
✔  functions: required API cloudbuild.googleapis.com is enabled
✔  functions: required API cloudfunctions.googleapis.com is enabled
✔  artifactregistry: required API artifactregistry.googleapis.com is enabled
i  functions: preparing codebase default for deployment

Error: There was an error reading .output/server/package.json:

.output/server/index.js does not exist, can't deploy Cloud Functions